/*
 * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package com.oracle.truffle.api.vm;

import java.util.LinkedList;

final class PolyglotThreadInfo {

    static final PolyglotThreadInfo NULL = new PolyglotThreadInfo(null);

    final Thread thread;

    private int enteredCount;
    final LinkedList<Object> explicitContextStack = new LinkedList<>();
    volatile boolean cancelled;

    PolyglotThreadInfo(Thread thread) {
        this.thread = thread;
    }

    boolean isCurrent() {
        return thread == Thread.currentThread();
    }

    void enter() {
        assert Thread.currentThread() == thread;
        enteredCount++;
    }

    boolean isPolyglotThread(PolyglotContextImpl c) {
        if (thread instanceof PolyglotThread) {
            return ((PolyglotThread) thread).isOwner(c);
        }
        return false;
    }

    void leave() {
        assert Thread.currentThread() == thread;
        --enteredCount;
    }

    boolean isLastActive() {
        assert Thread.currentThread() == thread;
        return thread != null && enteredCount == 1 && !cancelled;
    }

    boolean isActive() {
        return thread != null && enteredCount > 0 && !cancelled;
    }

    Thread getThread() {
        return thread;
    }

    @Override
    public String toString() {
        return super.toString() + "[thread=" + thread + ", enteredCount=" + enteredCount + ", cancelled=" + cancelled + "]";
    }

}
